Method of fabricating a bonded cascade assembly for an aircraft thrust reverser

ABSTRACT

A method of fabricating a bonded cascade assembly of a thrust reverser for an aircraft nacelle. The method may include inserting individual turning vanes between spaced apart elongated stiffeners at an aft end thereof and sliding the turning vanes toward a front frame piece attached to or integrally formed with forward ends of the elongated stiffeners. The elongated stiffeners may have inner and outer flanges for trapping and limiting radial movement of the turning vanes. The method may further include bonding the turning vanes to the structural frame with a structural adhesive and attaching a closeout cap to the aft ends of each of the elongated stiffeners.

RELATED APPLICATIONS

This patent application is a continuation application, and claimspriority benefit with regard to all common subject matter, ofearlier-filed U.S. patent application Ser. No. 14/305,444, filed on Jun.16, 2014, and entitled “METHOD OF FABRICATING A BONDED CASCADE ASSEMBLYFOR AN AIRCRAFT THRUST REVERSER”. The Ser. No. 14/305,444 patentapplication is a non-provisional, and claims priority benefit withregard to all common subject matter, of U.S. Provisional PatentApplication No. 61/837,032, filed on Jun. 19, 2013, and entitled “BONDEDCASCADE ASSEMBLY FOR AIRCRAFT THRUST REVERSER”. The identifiedearlier-filed non-provisional and provisional patent applications arehereby incorporated by reference in their entireties into the presentapplication.

BACKGROUND

Most commercial jet aircraft engines employ thrust reversers to aid instopping the aircraft during landing. Aircraft with under-wing-mountedengines typically use a translating sleeve cascade thrust reverser. Atranslating sleeve cascade thrust reverser includes an outer sleevecovering a fan duct portion of the engine. In use, the outer sleevetranslates in an aft direction, dropping down a series of doors to blockfan duct air and, in sequence, exposing a series of cascades or turningvanes that redirect the fan duct air outward and forward to reverse thethrust of the engine. The cascades may also feature side turning flowgeometry to prevent hot fan duct air impingement onto critical aircraftstructures. The cascades may be grouped and fixed together in severalcascade baskets or assemblies.

The individual cascade baskets are positioned radially around theengine's nacelle and are mounted to a fixed structure of the thrustreverser via a forward and aft mount or attach ring. While the fan ductair flows through the cascades, a pressure load is created on theirbaskets and ultimately reacted into the forward and aft mounts. Theindividual cascade baskets must provide sufficient stiffness to preventexcessive out of plane bending. Furthermore, if side turning flowgeometry is present, a lateral load will exist and the cascade basketsmust adequately resist “racking” loads. Cascade baskets aretraditionally fabricated using metals. Some cascade baskets are madefrom composite materials, which are generally lighter and more durable,but generally require a labor intensive fabrication that is moreexpensive than fabricating traditional metal cascade baskets.

Accordingly, there is a need for improved methods of fabricating cascadethrust reversers.

SUMMARY

Embodiments of the present invention provide a bonded cascade assemblyof a thrust reverser for an aircraft engine nacelle and methods offabricating the bonded cascade assembly. The bonded cascade assembly mayinclude a structural frame, a plurality of turning vanes, and a closeoutcap. The structural frame may include a plurality of elongatedstiffeners with forward and aft ends and a front frame piece attached toor integrally-formed with the forward ends of the elongated stiffeners.The turning vanes may each be positioned between two of the elongatedstiffeners, forming a cascade of turning vanes shaped and angled fordirecting airflow from within the nacelle in a generally outward andforward direction. The turning vanes may be attached to the elongatedstiffeners by structural adhesive and may also each have a geometryconfigured for cooperatively preventing or limiting radial movement ofthe turning vanes positioned therebetween. The closeout cap may beattached at the aft ends of the elongated stiffeners.

Other embodiments of the invention provide a method of fabricating abonded cascade assembly of a cascade thrust reverser of an aircraftengine nacelle. The method may include the step of inserting a pluralityof turning vanes between a plurality of elongated stiffeners at an aftend thereof and sliding the turning vanes toward a front frame pieceattached to or integrally formed with forward ends of the elongatedstiffeners. The elongated stiffeners may be held in spaced apart fromeach other by the front frame piece attached to or integrally formedwith the forward ends of the elongated stiffeners. The method mayfurther include the steps of bonding the turning vanes to the structuralframe with a structural adhesive and attaching a closeout cap to the aftends of each of the elongated stiffeners. The step of attaching thecloseout cap to the aft ends of the elongated stiffeners may includesliding the aft ends between pairs of positioning flanges of thecloseout cap and mechanically attaching the closeout cap and/or usingstructural adhesive to bond the closeout cap to the elongatedstiffeners.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the detaileddescription. This summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Other aspectsand advantages of the present invention will be apparent from thefollowing detailed description of the preferred embodiments and theaccompanying drawing figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a perspective view of an aircraft nacelle having a thrustreverser with bonded cascade assemblies constructed in accordance withan embodiment of the present invention;

FIG. 2 is a perspective view of one of the bonded cascade assemblies ofFIG. 1;

FIG. 3 is a cross-sectional elevation view of a structural frame of thebonded cascade assembly of FIG. 2;

FIG. 4 is a perspective view of the structural frame of FIG. 3;

FIG. 5 is perspective view of one of a plurality of turning vanes of thebonded cascade assembly of FIG. 2;

FIG. 6 is a cross-sectional perspective view of the turning vane of FIG.5;

FIG. 7 is a cross-sectional view of the bonded cascade assembly takenalong line 7-7 in FIG. 2;

FIG. 8 is a perspective view of a closeout cap of the bonded cascadeassembly of FIG. 2;

FIG. 9 is an exploded view of the bonded cascade assembly of FIG. 2;

FIG. 10 is a cross-sectional elevation view of an alternative embodimentof the structural frame configured for side-turning flow; and

FIG. 11 is a flow chart depicting steps in a method of fabricating abonded cascade assembly in accordance with an embodiment of the presentinvention.

The drawing figures do not limit the present invention to the specificembodiments disclosed and described herein. The drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the invention.

DETAILED DESCRIPTION

The following detailed description of the invention references theaccompanying drawings that illustrate specific embodiments in which theinvention can be practiced. The embodiments are intended to describeaspects of the invention in sufficient detail to enable those skilled inthe art to practice the invention. Other embodiments can be utilized andchanges can be made without departing from the scope of the presentinvention. The following detailed description is, therefore, not to betaken in a limiting sense. The scope of the present invention is definedonly by the appended claims, along with the full scope of equivalents towhich such claims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features being referred to areincluded in at least one embodiment of the technology. Separatereferences to “one embodiment”, “an embodiment”, or “embodiments” inthis description do not necessarily refer to the same embodiment and arealso not mutually exclusive unless so stated and/or except as will bereadily apparent to those skilled in the art from the description. Forexample, a feature, structure, act, etc. described in one embodiment mayalso be included in other embodiments, but is not necessarily included.Thus, the present technology can include a variety of combinationsand/or integrations of the embodiments described herein.

Embodiments of the present invention include a bonded cascade assembly10 and method of fabrication thereof. The bonded cascade assembly is acomponent of a thrust reverser 12 on an aircraft engine nacelle 14, asillustrated in FIG. 1. The bonded cascade assembly 10 may be disposedbetween a translating sleeve 16 and an engine (not shown) housed withinthe nacelle 14, and may have fore and aft ends 18, 20 fixedly attachedto fixed elements of the nacelle 14. As illustrated in FIG. 1, thethrust reverser 12 may have multiple bonded cascade assemblies 10,fabricated as described herein, which cooperatively circumscribe a fanexhaust duct of the nacelle 14. When the translating sleeve 16 istranslated aftward, the bonded cascade assembly 10 may function toredirect air within the nacelle 14 in a generally outward and forwarddirection.

As illustrated in FIG. 2, the bonded cascade assembly 10 may comprise astructural frame 22, a plurality of turning vanes 24, and a closeout cap26. The structural frame 22, turning vanes 24, and closeout cap 26 maybe formed of composite materials, such as those known in the art ofaircraft manufacturing. The turning vanes 24 are arranged in a cascadeconfiguration and secured to the structural frame 22 utilizingstructural adhesive. The closeout cap 26 is bonded or fastened to an aftend of the structural frame 22.

As illustrated in FIGS. 3 and 4, the structural frame 22 may comprise anelongated front frame piece 28 and a plurality of elongated stiffeners30 extending afterward from the front frame piece 28 and integrallyformed of one-piece construction therewith. Alternatively, the frontframe piece 28 may be formed separately and attached or bonded to theelongated stiffeners 30. The elongated stiffeners 30 may besubstantially parallel with each other and spaced a distance apart fromeach other. In some embodiments of the invention, the structural frame22 may be formed using resin transfer molding, compression molding, orpultrusion. Pultrusion, as used herein, is essentially the extrusion ofcomposite materials and is a term well-known in the art of compositemanufacturing. In some embodiments of the invention, some excessmaterial between the elongated stiffeners 30 may be cut after theformation thereof, leaving behind only enough material between thestiffeners to serve as the front frame piece 28, as illustrated in FIG.4.

The elongated stiffeners 30 may each have a front end 32 at which thefront frame piece 28 is integrally attached and an aft end 34 at whichthe turning vanes 24 are inserted into the frame structure 22 and thenslid forward, as later described herein. A length of the elongatedstiffeners 30 may extend substantially perpendicular to a length of thefront frame piece 28, as illustrated in FIG. 4. Furthermore, in someembodiments of the invention, the front frame piece 28 may have a slightcurve to its shape corresponding to a curve of the nacelle 14 to whichthe front frame piece 28 is mounted, as illustrated in FIG. 1.

The elongated stiffeners 30 may each have a configuration designed tocooperatively trap the turning vanes 24 in both radial andcircumferential directions relative to the nacelle 14. In someembodiments of the invention, each of the elongated stiffeners 30 mayhave inner and outer flanges 36,38 with a wall 40 or webbing extendingtherebetween. The inner and outer flanges 36,38 may be configured totrap the turning vanes 24 in the radial direction and provide aredundant load path in addition to the adhesive bonding of the turningvanes 24 to the structural frame 22. For example, the elongatedstiffeners 30 may have an I-beam configuration, as illustrated in FIG.3, or may alternatively present an hourglass shape or C-shaped channelsfor locating the turning vanes 24 therebetween. The inner and outerflanges 36,38 are preferably small (i.e., extend only a small distanceinto the space between the elongated stiffeners 30) compared with theoverall dimensions of the elongated stiffeners 30. In this way, theinner and outer flanges 36,38 have a minimal impact on weight andairflow of the bonded cascade assembly 10.

As illustrated in FIGS. 5 and 6, the turning vanes 24 may comprise anyflat, slanted, or curved configuration known in the art of cascadethrust reversers. The turning vanes 24 may be formed of compositematerial using any composite fabrication methods known in the art.Specifically, the turning vanes 24 may be injection molded, compressionmolded, transfer molded, or otherwise formed as a single piece and cutapart. Alternatively, the turning vanes 24 may be injection molded,compression molded, transfer molded, or otherwise formed individuallyand independently. A variety of molds could be used to form the turningvanes 24 and may be shaped to accommodate various flow featuresdetermined by aerodynamic analysis and tests for a particular aircraft.

The turning vanes 24 may each comprise a flow-directing portion 42slanted, curved, or otherwise configured for directing air from withinthe nacelle 14 in the forward and outward direction. The flow-directingportions 42 may each have inner edges 44, outer edges 46, opposing sideedges 48,50, a forward face 52, and an aftward face 54. The turningvanes 24 may further each comprise two positioning flanges 56,58integrally formed at the opposing side edges 48,50 of the flow-directingportion 42. The positioning flanges 56,58 may each have an inner edge60, an outer edge 62, a forward edge 64, an aftward edge 66, andopposing side faces 68,70.

The positioning flanges 56,58 may be configured to slide between theinner and outer flanges 36,38 of the structural frame's elongatedstiffeners 30, as illustrated in FIG. 7, with one of the faces 68,70 ofeach of the positioning flanges 56,58 abutting the wall 40 or webbing ofone of the elongated stiffeners 30. The inner and outer edges 60,62 ofthe positioning flanges 56,58 may abut the inner and outer flanges 36,38of the elongated stiffeners 30. Furthermore, when a plurality of theturning vanes 24 are slid into the structural frame 22, the forward andaftward edges 64,66 of their positioning flanges 56,58 may abut againsteach other. For example, the aftward edge 66 of the positioning flanges56,58 of a first one of the turning vanes 24 may abut the forward edge64 of the positioning flanges 56,58 of a second one of the turning vanes24 placed behind and adjacent to the first one of the turning vanes 24,as illustrated in FIGS. 2 and 9.

The geometric shape and size of the positioning flanges 56,58, such asthe angle at which the edges 60-66 of the positioning flanges 56,58meet, may affect the angle at which the flow-directing portions 42 arefixed within the structural frame 22, in addition to the actual shapeand location of the individual flow-directing portions 42 relative tothe positioning flanges 56,58. That is, the flanges 56,58 may beconfigured to properly clock the turning vanes 24 in the correctattitude during insertion and cure, due to the interaction of thepositioning flanges 56,58 with each other and the trapped geometrybetween components of the structural frame 22 and the closeout cap 26.Furthermore, in some embodiments of the invention, clocking features maybe molded, cut, or otherwise formed into the positioning flanges 56,58,such as mating indentions and protrusions, to assist in properlyaligning the turning vanes 24 relative to each other within thestructural frame 22.

The closeout cap 26, as illustrated in FIG. 8, may be molded orotherwise formed of a rigid material, such as composite material, andmay be configured to match the aft ends 34 of the elongated stiffeners30. Specifically, the closeout cap 26 may be compression molded,transfer molded, injection molded, pultruded, or otherwise integrallyformed of one-piece construction and may comprise an elongated strip 76of rigid material and a plurality of slots 78 formed therein. Forexample, the slots 78 may be formed directly in the elongated strip 76of the closeout cap 26 or formed by end cap flanges 80,82 extendingsubstantially perpendicularly from the elongated strip 76 and spacedapart by an amount corresponding to the size and configuration of theelongated stiffeners 30. In some embodiments of the invention, theelongated strip 76 of the closeout cap 26 may be slightly curved tocorrespond to the shape and/or curvature of the nacelle 14 to which thecloseout cap 26 is configured to be mounted.

In one alternative embodiment of the invention, as illustrated in FIG.10, the structural frame 22 may be replaced with an alternativestructural frame 122 having alternative elongated stiffeners 130 thatare angled or curved in a slightly sideways or circumferentialdirection. This configuration may direct some of the airflow from withinthe nacelle 14 in a circumferential or sideways direction. Thealternative structural frame 22 may require alternative turning vanes(not shown) with a matching curvature of side edges and/or flanges.

A method of fabricating the bonded cascade assembly 10, as illustratedin FIG. 9, may generally comprise individually forming the structuralframe 22, the turning vanes 24, and the closeout cap 26 from compositematerials and sliding the turning vanes 24 into the structural frame 22in an aft-to-forward direction toward the front frame piece 28. Then thecloseout cap 26 may be attached to an aft end of the structural frame22.

The flow chart of FIG. 11 depicts the steps of an exemplary method 1100for fabricating the bonded cascade assembly 11. In some alternativeimplementations, the functions noted in the various blocks may occur outof the order depicted in FIG. 11. For example, two blocks shown insuccession in FIG. 11 may in fact be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder depending upon the functionality involved.

As illustrated in FIG. 11, the method 1100 of fabricating the bondedcascade assembly 10 may first include a step of molding, injectionmolding, and/or pultruding composite material to form each of thecomponents of the bonded cascade assembly 10 described herein, asdepicted in block 1102. Next, the method 1100 may include the steps ofinserting the turning vanes 24 between the elongated stiffeners 30 atthe aft ends 34 of the elongated stiffeners 30, as depicted in block1104, and sliding the turning vanes 24 in a direction from the aft ends34 of the elongated stiffeners 30 toward the front frame piece 28, asdepicted in block 1106. As noted above, the elongated stiffeners 30 eachhave a geometry configured for cooperatively preventing or limitingradial movement of the turning vanes 24 slid therebetween. That is, theinner and outer flanges 36,38 or other protruding portions of theelongated stiffeners 30 may prevent radial movement of the positioningflanges 56,58 relative to the nacelle 14.

The method 1100 may further comprise the steps of bonding the turningvanes 24 to the structural frame 22 with the structural adhesive, asdepicted in block 1108, and attaching the closeout cap 26 to the aftends 34 of each of the elongated stiffeners 30, as depicted in block1110. Specifically, the structural adhesive may be applied onto thepositioning flanges 56,58 of the turning vanes 24 and/or the elongatedstiffeners 30 prior to steps 1002 and 1004, or may be otherwise injectedbetween the turning vanes 24 and the elongated stiffeners 30 after steps1002 and 1004. Once all the turning vanes 24 have been inserted andbonded to the elongated stiffeners 30, the closeout cap 26 is bonded ormechanically fastened to the structural frame 22 to close out the framestructure. For example, the aft ends 34 of the elongated stiffeners 30may be slid between adjacent pairs of the end cap flanges 80,82 andmechanically attached thereto or bonded thereto using structuraladhesive or any other method known in the art.

In some embodiments of the invention, the method 1100 may additionallyinclude the steps of mechanically mounting or otherwise attaching thefront frame piece 28 and the closeout cap 26 to fixed structuralelements of the nacelle 14 and/or thrust reverser 12, as depicted inblock 1112. The method 1100 may be repeated multiple times to form thethrust reverser 12, since the thrust reverser 12 may typically include aplurality of cascade assemblies.

Advantageously, the present invention provides most of the benefits of amonolithic composite cascade assembly utilizing a more automatedapproach to fabrication and presumably a lower cost product.Specifically, having the front frame piece integrally formed with theelongated stiffeners provides the strength of a monolithic cascadeassembly at the forward end, which experiences the most longitudinalload. Meanwhile, little to no longitudinal load is exerted at the aftend of the bonded cascade assembly, where the closeout cap is separatelyattached. Thus, the separately-formed turning vanes and closeout capalleviate the manufacturing complexities of a completely monolithiccascade assembly without sacrificing the strength of the monolithiccascade assembly.

Although the invention has been described with reference to thepreferred embodiment illustrated in the attached drawing figures, it isnoted that equivalents may be employed and substitutions made hereinwithout departing from the scope of the invention as recited in theclaims. For example, in some alternative embodiments of the invention,the front frame piece 28 could actually be the closeout cap 26, and theaft ends 34 of the elongated stiffeners 30 could have anintegrally-formed aft frame piece (not shown). In this alternativeembodiment, the turning vanes 24 could be inserted from the front ends32 of the elongated stiffeners 30 and slid toward this aft frame pieceduring fabrication of the bonded cascade assembly.

Having thus described various embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:
 1. A method of fabricating a cascade assembly, the methodcomprising: attaching a plurality of turning vanes to a structuralframe, the structural frame comprising a plurality of elongatedstiffeners each having forward and aft ends and inner and outer flangesbetween which at least portions of the turning vanes are located afterthe turning vanes are attached to the structural frame, the inner andouter flanges being configured for cooperatively preventing or limitingradial movement of the turning vanes positioned therebetween, and aframe piece attached to or integrally formed with the forward or aftends of the elongated stiffeners; and attaching a closeout cap to eachof the elongated stiffeners at the aft or forward ends opposite of theframe piece.
 2. The method of claim 1, wherein the elongated stiffenersand the frame piece are made of composite material integrally formed ofone-piece construction by molding or pultrusion.
 3. The method of claim1, wherein the turning vanes are formed of one-piece construction bymolding composite material.
 4. The method of claim 1, wherein thecloseout cap is made of composite material integrally formed ofone-piece construction by molding, injection molding, or pultrusion. 5.The method of claim 1, wherein the closeout cap comprises end capflanges configured for cooperatively preventing or limitingcircumferential movement of the elongated stiffeners positionedtherebetween during the step of attaching the closeout cap.
 6. Themethod of claim 1, wherein the closeout cap is bonded to the elongatedstiffeners with structural adhesive.
 7. The method of claim 1, whereinthe turning vanes comprise flow-directing portions with opposing sideedges and opposing positioning flanges extending forward and aft fromthe side edges of the flow-directing portions, wherein the elongatedstiffeners are configured to cooperatively trap the positioning flangescircumferentially and radially after the step of attaching the turningvanes and the frame piece and the closeout cap are configured tocooperatively trap the turning vanes therebetween after the step ofattaching the closeout cap.
 8. The method of claim 7, wherein thepositioning flanges comprise forward and aft edges configured to abutforward or aft edges of adjacent ones of the positioning flanges whenpositioned within the structural frame, such that a resulting trappedgeometry of the positioning flanges within the elongated stiffenersproperly clocks the flow-directing portions in a desired attituderelative to the structural frame.
 9. A method of fabricating a cascadeassembly of a cascade thrust reverser of an aircraft engine nacelle, themethod comprising: attaching turning vanes between elongated stiffenersof a structural frame, the elongated stiffeners each having forward andaft ends and inner and outer flanges or protruded portions between whichat least portions of the turning vanes are located after the turningvanes are attached between the elongated stiffeners, the inner and outerflanges or protruded portions being configured for cooperativelypreventing or limiting radial movement of the turning vanes relative tothe nacelle, the elongated stiffeners being spaced from each other via afront frame piece integrally-formed with the forward ends of theelongate stiffeners; and attaching a closeout cap to the aft ends ofeach of the elongated stiffeners.
 10. The method of claim 9, wherein theelongated stiffeners and the front frame piece are made of compositematerial integrally formed of one-piece construction by resin transfermolding, compression molding, or pultrusion, wherein the turning vanesare each individually formed of composite material by injection molding,compression molding, or transfer molding, wherein the closeout cap ismade of composite material integrally formed of one-piece constructionby compression molding, transfer molding, injection molding, orpultrusion.
 11. The method of claim 9, wherein the closeout capcomprises end cap flanges configured for cooperatively preventing orlimiting circumferential movement, relative to the nacelle, of theelongated stiffeners, wherein the step of attaching the closeout cap tothe aft ends of the elongated stiffeners further comprises positioningthe aft ends of the elongated stiffeners between pairs of the end capflanges.
 12. The method of claim 9, wherein the turning vanes eachcomprise flow-directing portions with opposing side edges and opposingpositioning flanges extending forward and aft from the side edges of theflow-directing portions, wherein the elongated stiffeners are configuredto cooperatively trap the positioning flanges circumferentially andradially relative to the nacelle after the turning vanes are attached tothe elongated stiffeners and the front frame piece and the closeout capare configured to cooperatively trap the turning vanes therebetweenafter the step of attaching the closeout cap.
 13. The method of claim12, wherein the positioning flanges comprise forward and aft edgesconfigured to abut forward or aft edges of adjacent ones of thepositioning flanges when positioned within the structural frame, suchthat a resulting trapped geometry of the positioning flanges within theelongated stiffeners properly clocks the flow-directing portions in adesired attitude relative to the structural frame.
 14. A bonded cascadeassembly of a cascade thrust reverser of an aircraft engine nacelle, thebonded cascade assembly comprising: a structural frame made of compositematerial and comprising: a plurality of elongated stiffeners each havinga forward end and an aft end, and a front frame piece integrally-formedwith the forward ends of the elongated stiffeners; a plurality ofturning vanes made of composite material and each positioned between twoof the elongated stiffeners and attached thereto; and a closeout capmade of composite material and attached at the aft ends of the elongatedstiffeners.
 15. The assembly of claim 14, wherein the elongatedstiffeners each further include an inner flange and an outer flange, theinner flanges and the outer flanges being cooperatively configured forpreventing or limiting radial movement of the turning vanes relative tothe nacelle.
 16. The assembly of claim 14, wherein the turning vaneseach comprise flow-directing portions with opposing side edges andopposing positioning flanges extending forward and aft from the sideedges of the flow-directing portions, wherein the elongated stiffenerscooperatively trap the positioning flanges circumferentially andradially relative to the nacelle, and the front frame piece and thecloseout cap cooperatively trap the turning vanes therebetween.
 17. Amethod of fabricating a cascade assembly, the method comprising:attaching a plurality of turning vanes to a structural frame, thestructural frame comprising a plurality of elongated stiffeners eachhaving forward and aft ends and C-channels or hourglass-shapedconfigurations configured for cooperatively preventing or limitingradial movement of the turning vanes, and a frame piece attached to orintegrally formed with the forward or aft ends of the elongatedstiffeners; and attaching a closeout cap to each of the elongatedstiffeners at the aft or forward ends opposite of the frame piece.